Granddaddy longlegs spiders, more commonly known as daddy longlegs, are not technically spiders. They have three segmented body parts instead of the two required of true spiders. They are especially active in the late summer and early fall --- earning them their other common name, harvestmen --- and can become a pest when they find their way inside your home through cracks and crevices. If you discover one of them in your home, treat it immediately before an infestation occurs.
Use a vacuum attachment to suck up any spiders or webs you see. Look for spiders and webs in dark, quiet places like attics, closets and basements.
Sprinkle some boric acid under appliances, around windows and doorways or anywhere you have seen granddaddy longlegs. Boric acid is a natural pesticide that is a highly effective insect killer.
Put some spider traps in areas you have seen granddaddy longlegs frequent. The traps contain bait that lures the spiders in and then traps them with glue. You can purchase these traps from your local home supply store.
Apply a residual insecticide to control granddaddy longlegs. Spray around your home and yard to keep them from entering your house.
Block entry points into your home. Seal cracks and crevices with caulk and use weather stripping for doors or windows in loose frames.
Take care when using insecticides and boric acid. Keep them out of the reach of pets and children.